Numbers 31:8

31:8 They killed the kings of Midian in addition to those slain – Evi, Rekem, Zur, Hur, and Reba – five Midianite kings. ¹  They also killed Balaam son of Beor with the sword. ² 

Joshua 13:21

13:21 It encompassed ³  all the cities of the plain and the whole realm of King Sihon of the Amorites who ruled in Heshbon. Moses defeated him and the Midianite leaders Evi, Rekem, Zur, Hur, and Reba (they were subjects of Sihon and lived in his territory). ⁴ 

[31:8]  ¹ sn Here again we see that there was no unified empire, but Midianite tribal groups.

[31:8]  ² sn And what was Balaam doing among the Midianites? The implication is strong. This pagan diviner had to submit to the revealed will of God in the oracles, but he nonetheless could be hired. He had been a part of the attempt to destroy Israel that failed; he then apparently became part of the plan, if not the adviser, to destroy them with sexual immorality and pagan ritual.

[13:21]  ³ tn The words “it encompassed” are supplied in the translation for clarification.

[13:21]  ⁴ tn Heb “princes of Sihon, inhabitants of the land.”